WO2011118451A1 - Method for producing spring - Google Patents

Abstract

In the provided method for producing a spring with a painted surface, the paint baking and low-temperature annealing are combined, and the time for said treatment is shortened. The production method has a heating step (S12) for heating the spring to a predetermined set temperature, and painting steps (S14, S16) for, while cooling the heated spring by a predetermined cooling pattern, spraying paint onto the surface of the spring and baking the spring. In addition, the set temperature in the heating step and the cooling pattern in the painting steps are set in a manner such that the spring is annealed at a prescribed low-temperature during the heating step and painting steps.

Description

Spring manufacturing method

This application relates to a spring manufacturing method. Specifically, the present invention relates to a technique for shortening a painting process for painting the surface of a spring.

Since the spring is fatigued due to repeated loads, the spring is subjected to a treatment for improving durability (for example, shot peening treatment). In addition, the surface of the spring is painted in order to prevent a decrease in life and deterioration of characteristics due to corrosion. For these reasons, in the conventional manufacturing method of the spring, first, a treatment for improving the durability of the spring (for example, shot peening) is performed, and then the paint is sprayed on the surface of the spring, and finally, the spray is sprayed. The paint is baked onto the spring (edited by the Spring Society of Japan “Spring” 4th edition, pages 522 to 530, Maruzen Co., Ltd.).

When a treatment for improving durability such as shot peening is performed on the spring, the spring sag increases. Therefore, it is preferable to perform a heat treatment to prevent the spring sag. Therefore, a heat treatment for baking the paint sprayed on the surface of the spring (ie, baking treatment) and a heat treatment for preventing the spring from sagging (ie, low temperature annealing treatment after shot peening (hereinafter, low temperature annealing) It is conceivable to shorten the process by combining the treatment))).

However, the paint sprayed on the surface of the spring has a unique baking coating temperature range, and it is necessary to perform baking treatment within that temperature range. For this reason, when the baking treatment and the low-temperature annealing treatment are combined, the temperature during the treatment is limited within the baking coating temperature range of the paint. The baking coating temperature range is usually lower than the temperature suitable for low temperature annealing treatment. As a result, when both the baking treatment and the low-temperature annealing treatment are used, there is a problem that the time required for the heat treatment becomes long.

This application aims at providing the technique which can shorten the processing time, combining the baking process and the low-temperature annealing process.

The spring manufacturing method disclosed in the present specification includes a heating step of heating a spring to a preset temperature, and spraying paint onto the surface of the spring while cooling the heated spring with a preset cooling pattern. It has a painting process of baking. The set temperature and cooling pattern are set such that a predetermined low-temperature annealing process is performed on the spring in the heating process and the painting process.

In this manufacturing method, the spring is heated to a set temperature, and the paint is sprayed and baked onto the surface of the spring while the heated spring is cooled. For this reason, the set temperature which heats a spring is not restrict | limited to the baking coating temperature range of a coating material, It can heat to the temperature higher than the temperature range, and a suitable low-temperature annealing process can be performed to a spring. On the other hand, even if the spring is heated to a temperature exceeding the coating temperature range, if the paint is sprayed on the spring surface after the spring temperature falls within the coating temperature range, the spring surface can be appropriately coated. . Therefore, the heat treatment that combines the baking treatment and the low-temperature annealing treatment can be performed in a short time.

In the above manufacturing method, the set temperature is preferably set in the range of 190 to 300 ° C. This is because if the set temperature is less than 190 ° C., the low-temperature annealing treatment becomes insufficient unless the low-temperature annealing treatment is performed for a long time, and the sag resistance deteriorates. On the other hand, if the set temperature exceeds 300 ° C., the low-temperature annealing process becomes excessive and the durability deteriorates.

In the above manufacturing method, it is preferable that the set temperature exceeds the upper limit of the baking coating temperature range of the paint. By setting the set temperature so as to exceed the upper limit of the baking coating temperature range, it is possible to shorten the time until the baking of the paint is completed.

When the set temperature exceeds the upper limit of the paint baking temperature range, the cooling rate for cooling the spring is preferably set in the range of 0.01 to 13.00 ° C./sec. More preferably, the cooling rate is set in the range of 0.50 to 4.50 ° C./second.

The flowchart which shows a part of manufacturing process of the spring of an Example. The figure which shows together the upper limit and lower limit of processing time when low temperature annealing processing is carried out at constant temperature. The figure which shows typically an example of the temperature profile between steps S12-S16. The figure which shows the other example of a temperature profile typically. The figure which shows the other example of a temperature profile typically. The figure which shows the other example of a temperature profile typically.

A method for manufacturing the spring according to this embodiment will be described. In this embodiment, a case where a stabilizer which is a kind of spring is manufactured will be described as an example. The stabilizer has a substantially straight linear portion and arm portions provided at both ends of the linear portion. When the stabilizer is mounted on the automobile, the arm portions at both ends of the stabilizer are fixed to the left and right wheels, while the linear portion is fixed to the vehicle body. As a result, rolling of the vehicle body during turning is suppressed, and driving stability of the automobile is improved.

In order to manufacture a stabilizer, first, a steel material is formed into a stabilizer shape by bending cold, warm or hot steel, a heat treatment step of heat-treating the steel material formed into the stabilizer shape, and the heat-treated steel material A shot peening process for shot peening on the surface of the steel and a coating process for coating the surface of the steel material after shot peening. Since the molding step and the heat treatment step can be performed in the same manner as in the prior art, detailed description thereof is omitted here. Hereinafter, the shot peening process and the coating process will be described in detail.

As shown in FIG. 1, first, shot peening is performed on the surface of the stabilizer heat-treated in the heat treatment step (S10). Thereby, compressive residual stress is applied to the stabilizer, and the durability of the stabilizer is improved. Further, the surface oxide scale formed on the surface of the stabilizer in the heat treatment step performed after the molding step is removed. As a result, the degree of painting can be improved. Note that the shot peening in step S10 can be performed by a method similar to the conventional method. In step S10, processing such as honing and blasting may be performed instead of shot peening.

Next, the stabilizer subjected to shot peening in step S10 is heated (S12). In this heat treatment, heating is performed until the surface temperature of the stabilizer reaches a preset temperature. The set temperature is preferably set in the range of 190 to 300 ° C. When the set temperature is lower than 190 ° C., the low-temperature annealing process becomes insufficient unless the baking process in step S16 described later is performed for a long time. If the low-temperature annealing treatment is insufficient, the processing strain that adversely affects the performance caused by the shot peening in step S10 is not sufficiently released, and the sag resistance is deteriorated. On the other hand, when the set temperature exceeds 300 ° C., if the baking process in step S16 is completed, the low-temperature annealing process becomes excessive. If the low-temperature annealing process is excessive, the compressive residual stress applied by the shot peening in step S10 is excessively released, and the durability deteriorates.

Here, since the heat treatment in step S12 is performed before painting on the stabilizer, the set temperature can be set to a temperature exceeding the upper limit of the baking coating temperature range of the paint. By heating the stabilizer beyond the upper limit of the baking coating temperature range of the paint in step S12, more effects of the low-temperature annealing treatment are imparted in the heating process of step S12, and as a result, the low-temperature annealing treatment is completed. Time can be shortened. Even if the set temperature exceeds the upper limit of the baked coating temperature range of the paint, no problem arises in this embodiment because the paint is sprayed onto the surface of the stabilizer after the surface temperature of the stabilizer has dropped to the baked paint temperature range.

Further, in the heating process of step S12, after the surface temperature of the stabilizer rises to the set temperature, it may be heated so as to be held at the set temperature for a predetermined time. Thereby, the surface temperature of the stabilizer can be made uniform. In this case, the holding time at the set temperature can be about 0 to 60 seconds. By setting the holding time to 60 seconds or less, the heating process is prevented from being prolonged.

It should be noted that various heating methods can be employed in the heating step of step S12 described above. However, in order to shorten the heating process in step S12, it is preferable to employ a heating method capable of rapid heating. As such a rapid heating method, for example, high-speed hot air heating (wind speed of 10 m / s or more), induction heating, infrared heating, electric heating, or the like can be used.

When the heating of the stabilizer in step S12 is completed, paint is then sprayed on the surface of the stabilizer (S14). For spraying the paint, for example, spray coating in which the paint is atomized and sprayed with high-pressure air can be used. The spray coating conditions can be, for example, a wind speed of 0.5 to 1.0 m / min and a spraying distance of 50 to 200 mm. Alternatively, the paint can be sprayed by electrostatic coating. The conditions of electrostatic coating can be performed, for example, with an electric charge of 40 to 100 kV, a wind speed of 0.5 to 1.0 m / min, and an air volume of 50 to 100 m ³ / min. By coating under such conditions, a coating film having a uniform thickness can be formed.

Note that the spraying of the paint in step S14 is performed after the surface temperature of the stabilizer falls within the paint baking temperature range. For this reason, when the surface temperature of the stabilizer exceeds the upper limit of the baking coating temperature range in step S12, cooling is performed until the surface temperature of the stabilizer falls within the baking coating temperature range, and then the paint is sprayed on the surface of the stabilizer. .

When the spraying of the paint on the stabilizer surface is completed, the paint sprayed on the surface of the stabilizer is then baked on the surface of the stabilizer (S16). For the baking of the paint, the heat applied to the stabilizer in the heating process of step S12 is used. Moreover, in step S16, it controls so that the surface temperature of a stabilizer falls according to a predetermined cooling pattern. Thereby, the surface temperature of the stabilizer is maintained within the baking coating temperature range of the paint, and the low-temperature annealing process is performed on the stabilizer and the paint baking process is performed.

That is, in the present embodiment, the set temperature in step S12 and the cooling pattern in steps S14 and 16 are set so that the low-temperature annealing process having an effect suitable for the stabilizer is performed. That is, the low-temperature annealing process for the stabilizer is performed both during the heating process in step S12 and during the coating process in steps S14 and S16. Therefore, when the set temperature in step S12 is high, a large amount of low-temperature annealing effect is imparted in step S12. For this reason, it is not necessary to provide many low temperature annealing effects in steps S14 and S16. Therefore, the cooling rate of steps S14 and 16 is increased and / or the processing time of step S16 is shortened so that the low-temperature annealing effect does not become excessive. Conversely, when the set temperature in step S12 is low, only a small amount of low-temperature annealing effect is imparted in step S12. For this reason, many low temperature annealing effects in steps S14 and S16 must be given. Therefore, the cooling rate of steps S14 and 16 is decreased and / or the processing time of step S16 is increased so that the low-temperature annealing effect is not insufficient.

As described above, in this embodiment, the processing time of step S16 can be shortened by increasing the set temperature of step S12. This will be specifically described with reference to FIG. In FIG. 2, the upper curve shows the upper limit time of low temperature annealing when the processing temperature is constant, and the lower curve shows the lower limit time of low temperature annealing when the processing temperature is constant. Further, the temperature T _H indicates the upper limit of the baking finish temperature, the temperature T _L represents the lower limit of the baking finish temperature. For example, if the processing temperature of low-temperature annealing is T, the upper limit time t ₂ becomes the low-temperature annealing, the lower limit time of low-temperature annealing becomes t _1. That is, when the low-temperature annealing treatment temperature is T, the treatment time must be in the range of t ₁ to t ₂ . When the process time exceeds t _2, low-temperature annealing effect becomes excessive, but the better the sag resistance, durability is deteriorated. On the other hand, if the treatment time is less than t _1, a low temperature annealing effect becomes insufficient, although better durability, sex is deteriorated sag resistance. As apparent from FIG. 2, the higher the processing temperature, the shorter the time for the low-temperature annealing processing. In particular, at a temperature exceeding the upper limit T _H (for example, 240 ° C.) of the coating temperature range, a desired low-temperature annealing effect can be imparted in a very short time. Therefore, by increasing the set temperature in step S12, the low temperature annealing effect imparted in step S12 can be increased, and the processing time in steps S14 and S16 can be shortened.

In step S16, since the paint must be baked on the surface of the stabilizer, the surface temperature of the stabilizer is set within the baking baking temperature range of the paint only for the time required for baking the paint. For this reason, the upper limit value of the cooling rate can be determined from the time required for completing the baking coating. For example, when the surface temperature of the stabilizer decreases linearly, when the baking coating temperature range is 240 to 160 ° C. and the baking time is 20 minutes, the maximum cooling rate is 80 ° C./20 minutes ( That is, 240 ° C./hour). Therefore, the cooling rate is determined in a range smaller than 240 ° C./hour.

Further, the cooling rate of the stabilizer in step S16 can be controlled by, for example, arranging the stabilizer in the hot stove and adjusting the temperature of hot air supplied into the hot stove. In this case, it is preferable that the range of the cooling rate of the stabilizer is 0.01 to 13.00 ° C./second. This is because if the cooling rate is less than 0.01 ° C./second, the processing time for low-temperature annealing becomes long. On the other hand, if the cooling rate is higher than 13.00 ° C./second, it is difficult to ensure a sufficient baking time. From the viewpoint of improving the coating quality, the cooling rate is preferably in the range of 0.50 to 4.50 ° C./second. By performing coating within this cooling rate range, variations in the surface temperature during coating can be suppressed within a range that is substantially free of problems.

Note that the temperature profiles (heating pattern and cooling pattern) in steps S12 to S16 can be, for example, the temperature profiles shown in FIGS. In the example shown in FIG. 3, first, the surface temperature of the stabilizer is heated to T ₁ (t ₁ to t ₂ ). Next, the stabilizer is cooled at a relatively high cooling rate (temperature reduction rate) until the surface temperature of the stabilizer reaches T ₂ (the upper limit value of the paint baking temperature range (T _{H in} the example of FIG. 2)) (t ₂ to t ₃ ) After that, paint is sprayed on the surface of the stabilizer (t ₃ to t ₄ ). When the paint is sprayed on the surface of the stabilizer, the baking process is performed for a predetermined processing time while controlling the cooling rate so that the surface temperature of the stabilizer maintains the baking coating temperature range (t ₄ to t ₅ ). The cooling rate (temperature decrease rate) of the stabilizer between the time t ₃ and t ₅ after the paint is sprayed on the surface of the stabilizer until the baking of the paint is finished is the cooling rate of the stabilizer between the times t ₂ and t ₃ Is made smaller. In the temperature profile shown in FIG. 3, since the surface temperature of the stabilizer is heated to a temperature T ₁ that exceeds the upper limit value of the baking coating temperature range, many low-temperature annealing effects performed between t ₁ and t ₃ can be imparted. . Therefore, the processing times t ₁ to t ₅ required for painting the stabilizer surface can be shortened.

In the example shown in FIG. 4, first, the surface temperature of the stabilizer is heated until it reaches T ₄ (t ₇ to t ₈ ). Next, the stabilizer is cooled so that the surface temperature of the stabilizer decreases at a constant cooling rate (temperature reduction rate) (t ₈ to t ₁₁ ). During this cooling, when the surface temperature of the stabilizer falls within the baking coating temperature range of the paint, the paint is sprayed on the surface of the stabilizer (t ₉ to t ₁₀ ), and then the paint sprayed on the surface of the stabilizer is baked (t ₁₀ to t ₁₁ ). Also in the temperature profile shown in FIG. 4, as in the example shown in FIG. 3, the processing times t ₈ to t ₁₁ required for painting the surface of the stabilizer can be shortened.

Note that the temperature profile shown in FIG. 3 described above can be changed to the temperature profile shown in FIG. In the temperature profile shown in FIG. 5, the cooling rate (temperature reduction rate) of the stabilizer during the period from the time t ₃ to t ₄ until spraying of the paint is finished after the paint is sprayed on the surface of the stabilizer is set to 0 (that is, 3 is different from the temperature profile shown in FIG. 3 in that the surface temperature of the stabilizer is maintained constant. Even in such a temperature profile, since the surface temperature of the stabilizer is heated to a temperature T ₁ exceeding the upper limit value of the baking coating temperature range, the processing times t ₁ to t ₄ required for painting the surface of the stabilizer are It can be shortened.

Furthermore, the above-described temperature profile shown in FIG. 4 can be changed to the temperature profile shown in FIG. In the temperature profile shown in FIG. 6, the surface temperature of the stabilizer is heated until it reaches T ₄ (t ₇ to t ₈ ), and then the surface temperature of the stabilizer is maintained at T ₄ for a predetermined time (t ₈ to t _{8 ′} ). This is different from the temperature profile shown in FIG. By setting it as such a temperature profile, the surface temperature of a stabilizer is equalized and the coating quality of a stabilizer can be improved. Note that the time (t ₈ to t ₈ ) for soaking the surface temperature of the stabilizer as shown in FIG. 6 can be provided for each of the temperature profiles of FIGS.

As described above in detail, in the stabilizer manufacturing method of the present embodiment, the stabilizer is heated to a temperature exceeding the upper limit of the baking baking temperature range of the paint before coating, and the paint is applied to the surface of the stabilizer while cooling the stabilizer. Spray the paint on the surface of the stabilizer. Even when the stabilizer is heated to a temperature exceeding the upper limit of the baking coating temperature range of the paint, since the low-temperature annealing treatment is performed on the stabilizer, the low-temperature annealing effect that must be performed when baking the paint can be reduced. Thereby, the processing time required for painting the surface of the stabilizer can be shortened.

Although the present embodiment has been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
For example, in the above-described embodiment, the stabilizer is manufactured. However, the technology according to the present application can be applied to a case of manufacturing a spring other than the stabilizer. In particular, it can be suitably applied to a spring that is subjected to shot peening and painting. Examples of such a spring include a coil spring and a torsion bar.
In order to make the coating quality uniform, the surface temperature of the spring may be measured with a thermograph, and the coating may be performed from a portion where the surface temperature of the spring becomes an appropriate temperature. By making the temperature at which paint spraying starts constant, it is possible to prevent uneven coating and improve coating quality.

The technical elements described in the present specification or drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

Claims (6)

A method of manufacturing a spring comprising:
A heating step of heating the spring to a preset temperature set in advance;
A coating process of spraying and baking paint on the surface of the spring while cooling the heated spring with a preset cooling pattern,
The method for manufacturing a spring, wherein the set temperature and the cooling pattern are set such that a predetermined low-temperature annealing process is performed on the spring in the heating process and the painting process. The method for manufacturing a spring according to claim 1, wherein the set temperature is set in a range of 190 to 300 ° C. The method for manufacturing a spring according to claim 2, wherein the set temperature exceeds an upper limit value of a baking coating temperature range of the paint. The method for manufacturing a spring according to claim 3, wherein in the painting step, a cooling rate for cooling the spring is set in a range of 0.01 to 13.00 ° C / second. The method for manufacturing a spring according to claim 4, wherein the cooling rate is set in a range of 0.50 to 4.50 ° C / second. Before the heating step, further has a shot peening step of shot peening on the surface of the spring,
The spring manufacturing method according to any one of claims 1 to 5, wherein the predetermined low-temperature annealing treatment is a heat treatment for preventing spring sag.

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